1. Field of the Invention
The present invention relates to a sample measurement method and measurement sample base material and, more particularly, to a sample measurement method by an electron microscope, and more specifically, by a transmission electron microscope and a measurement sample base material.
2. Related Background Art
Fluorescent X-ray analysis is widely used for thickness measurement or composition analysis of thin films (reference D1). X-ray diffraction analysis or electron diffraction analysis is known as a method of evaluating the crystal structure of a thin film.
To measure the thickness of a thin film by fluorescent X-ray analysis, it is necessary to accurately know the density of the thin film. However, accurate measurement is difficult because the actual density is often different from the reference value. When the thin film as a sample to be measured is a multilayered film, the X-ray dose from each layer must accurately be estimated. If the layers contain the same element, accurate thickness measurement or composition analysis is difficult.
When crystal structure analysis is executed for a multilayered film as a sample by using X-ray diffraction analysis, peaks overlap, and discrimination is difficult. If the sample is very thin, the peak intensity is low and hard to detect.
When a TEM (Transmission Electron Microscope) is used, the thickness of a sample can more accurately be measured because the transmission image of the sample is observed by using an electron beam. In addition, when the electron beam diffraction function of the TEM is used, the crystal structure can be evaluated at a high spatial resolution. The crystal structure of a multilayered film or a very thin film can also be evaluated. When an energy dispersive analyzer attached to the TEM is used, the composition of a sample can also be analyzed.
To execute thickness measurement or crystal structure evaluation of a sample by using the TEM, the sample needs to be so thin that an electron beam can pass through it. As is known, a sample for a TEM is prepared by using ion milling or an FIB (Focused Ion Beam) method.
Conventionally known references are D1: “Device Analysis Guidebook”, edited by Japan Society for Analytical Chemistry, Maruzen Co., Ltd., Jul. 10, 1996, p. 138, p. 142, D2: “Transmission Electron Microscope”, edited by Surface Science Society of Japan, Maruzen Co., Ltd., Apr. 15, 2001, pp. 33–42, D3: “Japanese Patent Laid-Open No. 5-231997”, and D4: “Japanese Patent Laid-Open No. 10-19751”.